Diseases such as cancer, rheumatism and arthritis are often associated with severe pain. The pain disorder usually has a negative influence on the progression of the primary disease, e.g. cancer, which is the original cause of the pain. The range of pain felt by tumor patients comprises pain of the periosteum and of the bone itself, as well as visceral pain and pain in soft tissues. Severe pain brings the patient to the edge of his physical and emotional endurance and leads to depressive moods, irritability, weakness, restricted range of interests and reduced social activities. Successful pain therapy resulting in a lasting improvement of quality of life for the patient is therefore equally important to the success of a comprehensive therapy, as is the treatment of the actual causes of the disease.
Opioid analgesics take a central role in treating pain, especially chronic pain. The group of opioid analgesics comprises morphine, oxycodone, hydromorphone, nicomorphine, dihydrocodeine, diamorphine, papavereturn, codeine, ethyl morphine, phenyl piperidine and derivatives thereof, methadone, dextropropoxyphene, buprenorphine, pentazocine, tilidine, tramadol and hydrocodone. The pronounced pain-relieving effect of opioid analgesics is due to the imitation of the effect of endogeneous, morphine-like acting substances, whose physiological function is to control the reception and processing of pain stimuli.
Opioid analgesics are considered to be strong agonists if they bind with high affinity to opioid receptors and induce a strong inhibition of pain reception. Substances that also bind with high affinity to opioid receptors, but do not cause a reduction of pain reception and which thereby counteract the opioid agonists, are designated as antagonists. Depending on the binding behavior and the induced activity, opioids can be classified as pure agonists, mixed agonists/antagonists and pure antagonists.
Pure opioid antagonists comprise for instance naltrexone, naloxone, nalmefene, nalorphine, nalbuphine, naloxoneazinen, methylnaltrexone, ketylcyclazocine, norbinaltorfimine, naltrindol, 6-β-naloxol and 6-β-naltrexol. Further opioid agonists and antagonists are e.g. disclosed in W. Forth, D. Henschler, W. Rummel, K. Starke: Allgemeine und Spezielle Pharmakologie und Toxikologie, 7th edition, 1996, Spektrum Akademischer Verlag, Heidelberg, Berlin, Oxford.
Due to their analgesic efficacy, compounds such as oxycodone, tilidine, buprenorphine and pentazocine have been used in the form of medicaments for pain therapy. Medicaments such as Oxygesic® comprising oxycodone as the analgesic active compound and Valoron® comprising tilidine as the analgesic active compound have proven valuable for pain therapy.
Although opioids are effective in the management of pain, there is a risk of abuse by individuals who are dependent on opioids or who misuse opioids for non-therapeutic reasons. Besides the abuse potential of opioids, the use of potent opioid analgesics for pain therapy may lead to undesirable side effects such as constipation, breath depression, sickness and sedation. Attempts to minimize the addictive and habit-forming potential of opioid analgesics as well as their other side effects may involve the administration of antagonists which counteract the opioid analgesic. Such antagonists may be selected from naltrexone or naloxone. For example, this therapeutic concept has been successfully applied in a combination product ValoronN® of the opioid tilidine and the opioid antagonist naloxone, which is a commercially available intravenous narcotic antagonist indicated for blocking exogenously administered opioids.
WO 03/084520 describes a storage-stable pharmaceutical preparation comprising oxycodone and naloxone for use in pain therapy, with the active compounds being released from the preparation in a sustained, invariant and independent manner. In particular, it is stated therein that by the combination of oxycodone and naloxone an efficient analgesic activity and at the same time, the suppression of common side effects such as constipation, breath depression and development of addiction is achieved.
In diagnosing and treating patients for varying levels of side effects such as constipation caused by pain treatment with opioids, health care providers are constantly faced with difficulties, since the patients are not able to accurately describe the side effects that they are experiencing. The lack of a uniform system for the patients to use in describing opioid bowel dysfunction (OBD) syndromes such as constipation often presents a health care provider with very different descriptions for the same levels of constipation. These different descriptions sometimes result in ineffective, inadequate or excessive treatment. In addition, the lack of a uniform system for the patients to use in describing their incomplete bowel function results in an inaccurate medical record and inability to describe the bowel function in the course of treatment accurately for clinical studies or insurance providers.
Reduced bowel function, in particular constipation, may be a significant problem with patients receiving narcotic analgesics. It is known that some often-used parameters, like stool frequency and stool consistency do not fully reflect the impairment of patient satisfaction caused by constipation. It is generally agreed that the judgment by the patient could be more meaningful than e.g. the number of bowel movements. Subjective factors that may influence patient satisfaction include among other things hard stools, cramping, difficulty of defecation, incompleteness of bowel evacuation and painful laxation.
Health care providers are constantly looking for new and better methods to properly assess bowel function, in particular of patients receiving treatment with narcotic analgesics.